The reaction according to the invention falls under the category of reactions classified as the Ullmann condensation reaction.
The Ullmann condensation reaction is a process in which an aromatic amine is reacted with an aromatic halogen compound, preferably an aromatic iodide, in the presence of a base and a copper catalyst to synthesize an arylamine. It was discovered by F. Ullmann. (See, for example, F. Ullmann, Chemische Berichte., 1920, Vol. 36, p. 2382.)
This reaction has generally required a prolonged reaction time and necessitated a high temperature of usually 200° C. or higher for attaining a practical rate of arylation. Because of this, by-products generate in large amounts as a result of the oxidation, disproportionation, dimerization reaction, etc. of the reaction product. Although raw materials for electronic materials or intermediates therefor are generally required to have a high purity, purification by the removal of these by-products is exceedingly difficult and has posed a serious problem. In addition, there have been drawbacks leading to a cost increase, for example, that the reaction proceeds efficiently only when an iodized aromatic compound, which is more expensive, is used as the aromatic halogen compound to be reacted with an aromatic amine, and that an apparatus usable for the high-temperature reaction is necessary.
Methods for causing the reaction to proceed efficiently and inhibiting the generation of by-products have been attempted. For example, a process for triarylamine production which comprises reacting an aromatic amine compound with an iodized aromatic compound without using a solvent or in an inert hydrocarbon solvent in the presence of a copper catalyst and potassium hydroxide (JP-B-01-29182), processes for triarylamine production in which a surfactant such as a crown ether or polyethylene glycol is added (see JP-A-11-87061, JP-A-2000-178237, JP-A-2000-273068, and JP-A-2000-256276), and the like have been proposed. However, these processes also are not fully satisfactory in purity and the problem concerning the use of an iodized aromatic compound still remains unsolved.
For producing an arylamine compound having a high purity, it is preferred to conduct the reaction at a lower temperature. Processes for producing a triarylamine compound have been proposed which comprise reacting an aromatic amine compound with an iodized aromatic compound in an aromatic solvent in the presence of a copper catalyst, potassium hydroxide, and a tertiary amine compound at 120-150° C. (see JP-A-9-323958, JP-A-9-323959, JP-A-10-212267, JP-A-10-212268, JP-A-10-212269, and JP-A-10-312073). However, these processes also have been unsatisfactory in both yield and purity and necessitated a high degree of purification. Furthermore, in these processes also, it is necessary to use an expensive iodized aromatic compound because use of an inexpensive chlorinated aromatic compound or brominated aromatic compound therein results in a low yield and these compounds are hence unusable. Namely, these processes still have the problem concerning cost.
Furthermore, processes for producing nitrodiphenylamine at low cost from a halogenated nitrobenzene and an aniline derivative in the presence of a copper catalyst and an ammonium salt or phosphonium salt (see JP-A-57-40445) or in the presence of a copper catalyst and a phosphonium salt (see patent document 13) through the Ullmann reaction have been proposed. However, these are specialized processes for obtaining nitrodiphenylamine from a reactive halogenated nitrobenzene and are unsuitable for the synthesis of various arylamines by techniques of organic chemistry. In addition, since the nitrodiphenylamine obtained as the target compound does not have a high purity, these processes are not satisfactory when used for producing at low cost a high-purity arylamine, in particular a triarylamine or diarylamine, which is useful as a raw material for electronic materials or as an intermediate therefor.
Moreover, a process has been proposed in which a chlorinated aromatic compound or brominated aromatic compound is reacted with an aromatic amine compound in an aromatic solvent in the presence of a palladium catalyst, phosphine compound, and base at 20-140° C. (see JP-A-10-139742, JP-A-10-195031, JP-A-10-310561, JP-A-11-5769, Angewante Chemie. International English ed., 1998, Vol. 37, pp. 2046-2047, J. Am. Chem. Soc., 1998, Vol. 120, pp. 9722-9723, J. Org. Chem., 1996, Vol. 61, p. 1133, and Tetrahedron Letters, 1995, Vol. 36, No. 21, pp. 3609-3612). However, since palladium compounds are exceedingly expensive, the process proposed is not an industrially advantageous process. The process has been unsatisfactory also in yield and purity.